The invention relates to an air mass flowmeter for measuring the air mass taken in by the internal combustion engine.
Air mass flowmeters in the intake duct or charge duct of the internal combustion engine are known. They serve to measure the mass flow or the intake/charge air, in order to be able to determine and control the mass ratios accordingly during the chemical process of combustion.
An air mass flowmeter is known from EP 0 908 704 A1 that measures the air flow thermally. The air mass flowmeter is arranged with one end in a principal air stream in the intake duct to the internal combustion engine. A specific proportion of the principal air stream is directed into a first channel that leads to an air mass sensor. The air mass sensor determines thermally the air mass passing by it. The air stream is then diverted and channeled back into the principal air stream in order to be fed to the combustion operation. One disadvantage of the known air mass sensor is that the air flow is separated from the inner channel wall. Such separation causes the measurement signals of the downstream air mass sensor to be disturbed. It has proven that the position of the point of separation from the inner channel wall can vary significantly even with strong flows. Even small disturbances to the flow conditions result in major displacement of the position of the point of separation. The changing point of separation from the inner channel wall however results in areas with a separated flow of different sizes and positions.